One such valve is disclosed in, for example, Patent Document 1. FIG. 6 shows an example of a conventional pressure reducing valve. As illustrated in the drawing, the conventional pressure reducing valve includes a valve chamber 101, a pressure regulating chamber 102, and a partition member 110 for separating the valve chamber 101 and the pressure regulating chamber 102 from each other. High-pressure gas flows into the valve chamber 101 from an upstream side of the pressure reducing valve. The pressure regulating chamber 102 reduces the pressure of the high-pressure gas. A communication hole 111, which ensures communication between the valve chamber 101 and the pressure regulating chamber 102, is formed in the partition member 110. The portion of the partition member 110 facing the valve chamber 101 is a valve seat 112.
A body portion 121 of a valve body 120 is arranged in the valve chamber 101. The valve body 120 is movable and selectively approaches and separates from the valve seat 112. A rod section 122 extends from a distal end of the body portion 121. The rod section 122 extends into the pressure regulating chamber 102 through the communication hole 111. A communication line 105 is formed between the peripheral wall of the communication hole 111 and the rod section 122. After having flowed into the valve chamber 101, the gas flows into the pressure regulating chamber 102 via the communication line 105.
When the body portion 121 of the valve body 120 is received by the valve seat 112 of the partition member 110, the communication line 105 is closed by the valve body 120. This restricts flow of the gas from the valve chamber 101 to the pressure regulating chamber 102. When the body portion 121 of the valve body 120 separates from the valve seat 112, the communication line 105 becomes open. This permits the flow of the gas from the valve chamber 101 into the pressure regulating chamber 102. The pressure of the gas is reduced to a certain pressure in the pressure regulating chamber 102 before the gas flows downstream out of the pressure reducing valve.
With reference to FIG. 7, when the body portion 121 of the valve body 120 is received by the valve seat 112, the valve seat 112 receives load from the body portion 121. This plastically deforms the valve seat 112, as shown in FIG. 8, thus causing a portion of the peripheral wall of the communication hole 111 to project toward the axis of the communication hole 111. As a result, the cross-sectional communication area of the communication line 105 in the vicinity of the valve seat 112 is decreased. In this case, turbulence occurs in the flow of the gas in the communication line 105. The pressure loss of the gas flowing in the communication line 105 thus increases, making it likely that the pressure reducing valve will generate noise.